disabling form elements with array names

[mistergoomba]

my form looks like this:

<select name="name[sel]">
<option value="other">OTHER</option>
<option value="martin">Martin</option>
</select>

<input type="text" name="name[txt]">

now when the user selects OTHER, it will disable the text input. changing the names of the variables is not an option, and using this.form.elements[1].disabled is not an option.

the question is, how do i reference name[txt] in javascript to disabled the field?!